New windscreen: why the camera needs calibrating

In the housing by the rear-view mirror, many newer cars carry one or two cameras looking forward at the road. They supply the images for lane keeping and lane departure warning, traffic sign recognition, automatic high beam and in many cases the emergency braking assistant. Next to them there is often a rain and light sensor, and on some models a laser sensor for low-speed emergency braking.

The camera is not the only eye. Adaptive cruise control, and often the emergency braking assistant too, uses a radar sensor behind the badge or in the bumper; blind-spot warning uses radar sensors in the rear corners; a surround-view system uses cameras in the door mirrors, grille and tailgate. Many systems combine data from several sensors.

All these sensors have one thing in common: they need to know where they are looking relative to the car. The camera calculates distances and the course of lane lines from its image. If it is rotated or tilted by a small angle, the calculated lane is off, and an obstacle appears nearer or further away than it is. Calibration is the process of teaching the control unit this position.

Which jobs require calibration is set by the manufacturer for each model in its repair instructions. Some systems report a missing calibration themselves, with a message on the display or by switching off. You cannot rely on that: a camera that is slightly off target often carries on working — just inaccurately.

The typical triggers are much the same across almost all manufacturers:

There are two methods, and many manufacturers specify one, the other, or both in sequence for a given model. In static calibration the car stands on a level area in the workshop. A target board with a precisely defined pattern is set up in front of it at a specified distance and height, aligned with the thrust line. The workshop starts the routine through the diagnostic tool, and the camera learns from its image of the board where it is looking.

The conditions have to be right: tyre pressures to specification, car unladen, floor level, lighting even, enough room in front of the car. Static calibration is therefore a job for a workshop with a properly equipped bay, not something to improvise at the roadside.

In dynamic calibration a mechanic drives with the diagnostic tool connected — or the system learns by itself — along roads with clearly visible markings at a specified speed until the camera has collected enough reference points. That depends on the weather, the traffic and the state of the road markings, so it does not always take the same time.

The order matters: if both a wheel alignment and a calibration are due, the alignment comes first, then the camera. Done the other way round, the camera's reference line is wrong again once the alignment has been adjusted.

The same model often has many windscreen variants: with or without a camera bracket, with a heated camera area, with acoustic interlayer, with a wedge interlayer for a head-up display, with a heat-reflective coating, with cut-outs for sensors. The correct variant can be identified from the VIN; include it when you ask for an appointment.

Besides the carmaker's own glass there are windscreens from other glass manufacturers built for the same variant. That can work well if the bracket, the optical quality in the camera area and the specification are right. Ask the workshop which screen it will fit and whether calibration with that screen usually succeeds on your model; some carmakers expressly recommend their own glass for cars with cameras.

And the windscreen is more than glass. On many cars it contributes to the stiffness of the body, and the passenger airbag braces against it when it deploys. So the adhesive needs time before the car may be driven again. How long depends on the adhesive and the conditions; the workshop will tell you.

In Carvexia's garage directory you can search by place and service and send an appointment request. Say in the description that your car has a forward camera, give the VIN, and state that you expect the calibration with a report. The garage confirms the appointment, proposes another time or declines; prices on a profile are the garage's own figures.

An invoice for a windscreen replacement on a car with a forward camera should list the calibration as a separate item, together with the method used. If it is missing, ask before you pay. A windscreen swap without calibration is quicker and cheaper, and that is exactly why it happens. Whether glass cover pays for the calibration depends on the policy; settle that before the appointment, not afterwards.

Afterwards the papers belong in the car's folder. When you sell, they prove the job was done completely, and after an accident in which an assistance system played a part, they answer a question nobody else can. On the invoice or attached to it you should find:

When buying used, the first question is whether the windscreen is original. In one corner of every pane, the glass manufacturer and a date code are printed. If the windscreen differs clearly from the side windows — a different maker, a later date — it has been replaced. After a stone chip that is nothing unusual. It is simply the moment to ask for the invoice showing the calibration.

On a test drive a poorly calibrated camera gives itself away through its behaviour. The lane keeping assistant does not hold the car in the middle but closer to one line, or intervenes where there is nothing to correct. Traffic sign recognition misreads signs or misses them entirely, the high-beam assistant dips too late, the emergency braking assistant warns for no reason or too late. Any one of these can have other causes; several together are a clear hint.

Watch too for messages on the display saying a system is restricted or unavailable, and ask how long they have been appearing. A fault memory scan also shows assistance system entries that are not currently on the display. And look at the glass itself: a crooked trim strip, adhesive residue at the edge or a camera housing that does not sit cleanly are signs the job was not done with the necessary care.